PERIODICITY

• Who developed the periodic table?

  Dmitri Mendeleev
• How is the periodic table arranged?

  By atomic number ( protons)
• What did Dmitri Mendeleev notice?

  patterns in reactivity
• Lanthanides


  form 3+ ions

  similar reactivity
• Actinides


  manmade radioactive elements

  only thorium and uranium occur naturally
• Different blocks on periodic table

  
• explain why certain elements in the periodic table are classified as p block elements

  elements in the p block have their outer electrons in p orbitals
• atomic radius across group 3

  -decreases

  - due to increased nuclear charge

  - greater attraction between nucleus and electrons so electrons pulled closer
• atomic radius down a group

  -increases

  - electron shell is added

  - increase in shielding

  - attraction between electrons and nucleus is weaker
• nuclear charge across group 3

  increases
• Ionisation energy across a period

  -Increases

  -greater nuclear charge and similar shielding and smaller atomic radius

  - more energy required to remove electron
• ionisation energy down a group

  -decreases

  - attraction between nucleus and electrons decreases

  - shielding increases

  - atoms are bigger

  - less energy needed to remove the electron
• bp and mp of period 3

  increases from Na to Al due to metallic bonding

  silicon is the highest as its a giant covalent and then after si it decreases as they are simple molecular
• how to increase strength of metallic bonding


  - increase charge

  - smaller ion

  - more delocalised electrons
• structure of metals

  giant metallic structure

  very strong forces of electrostatic attraction between positive metal ions and negative delocalised electrons
• structure of non metals

  - simple molecular

  - van der Waals
• explain in terms of crystal structure and bonding why silicon (IV) oxide has a higher melting point than phosphorus (V) oxide

  -Silicon has a giant covalent structure (1)

  -Phosphorus has a simple molecular structure (1)

  -To melt silicon strong covalent bonds need to be broken / overcome (1)

  -To melt phosphorus weaker intermolecular (Van der Waals forces) need to be overcome (1)

  -(So it takes much more energy to melt silicon than to melt phosphorus (1))
• Explain why the melting point of sulfur (S8) is greater than that of phosphorus (P4).

  - Both s8 and p4 have simple molecular structures

  -To melt the weak intermolecular forces need to be overcome

  -As s8 is a bigger molecule it has stronger intermolecular forces (1)

  -This takes more energy to overcome (1)

  -and so s8 has a higher melting point
• explain why the melting point of aluminium is higher than melting point of sodium

  - al has bigger charge

  - there are more delocalised electrons

  - stronger metallic bonding
• explain why the atomic radius decreases across period 3 from Na to Cl

  -number of protons increase

  - shielding is similar
• identify the period 2 element from carbon to fluorine that has the largest atomic radius. explain your answer

  - carbon

  - fewer protons / smallest nuclear charge

  - similar shielding
• sodium fluoride contains sodium ions and flouride ions. explain why fluoride ion is larger than a sodium ion

  -fluoride ion has fewer protons / lower nuclear charge

  - weaker attraction between nucleus and outer electrons
• state the meaning of the term periodicity

  the repeating pattern of physical or chemical properties
• explain the dip between Mg and Al in ionisation energy

  -Mg has its outer

  electrons in the 3s sub shell,

  -Al is starting to fill the

  3p subshell.

  - 3p electrons are higher in energy.

  - so easier to remove
• explain the dip between P and S in ionisation energy

  -P has 3 3p electrons all singly in each orbital,

  - S has 4 3p electrons, starting to pair,

  - pairing repels so easier to remove when there is repulsion
• describe the graph of bp of period 3 elements

  increases from Na to Al, peak at Si, drops to P4, higher again for S8 then drops for Cl2 and lowest at Ar
• which period 3 element has the highest boiling point?

  silicon
• structure and bonding of Na, Mg, Al?

  metallic lattice.strong electrostatic force of attraction between positive ion and delocalised electrons.
• why does boiling point increase from Na to Mg to Al?

  nuclear charge increases, atomic radius gets smaller and more delocalised electrons so greater attraction
• what is the structure and bonding of Si and why does it have the highest boiling point?

  giant covalent. strong covalent bonds which take a lot of energy to overcome
• what type of molecules are P4, S8, Cl2?

  simple molecular
• why are the boiling points of the simple molecular elements lowest?

  need to break the weak van der waals forces between molecules
• what structure is Ar?

  monatomic
• describe and explain the trend in electronegativity across period 3

  increases.

  • nuclear charge increases
  • atomic radius decreases.
  • shielding is constant
  • so greater attraction between electron pair and positive nucleus so greater power to attract in a covalent bond.